Safety blasting device



Nov. 3, 1931. F. H. ARMSTRONG 1,829,847

SAFETY BLASTING DEVICE Filed Nov. 2. 1929 2 Sheets-Sheet 2 @y www 7%/ P12/Vgl?, V

EXPLOSIVE DEVICES Patented Nov. 3, 1931 UNITED STATES 'PATENT OFFCE FRANK H. ARMSTRONG, OF CHICAGO, ILLINOIS, ASSIGNOR TO SAFETY MINING COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION SAFETY BLASTING DEVICE Application filed November 2, 1929. Serial No. 404,474.

This invention relates to the recently developed safety type of blasting device wherein the blasting medium is an expansive noncombustible gas. A device of this general type is illustrated in the patent to Helmholtz et al., No. 1,723,351.

The invention has for its object the simplification and refinement of blasting devices of the type indicated.

It is also an object of the invention to provide a device of this type having improved-A safety and reliability characteristics.

Another object of the invention is to provide a blasting cartridge wherein the charging and discharging operations are rendered extremely simple.

A further object is to provide a cartridge construction and design which may be manufactured and maintained at substantially less cost than cartridges heretofore produced.

These objects are attained by the present invention, an illustration of which is found in the accompanying drawings.

Figure 1 is a view in longitudinal section of a portion of a blasting cartridge constructed in accordance with my invention.

Figure 2 is an end View of the cartridgr` showing the protector disc with cover plates in closed position.

Figure 3 is a View similar to Figure 2 but showing the cover plates in open position..

Figure 4 is a view in transverse section taken along line 4 4 of Figure l.

Figure 5 is a detail view of the valve.

Figures 6, 7, 8 and 9 are detail views of the contact plug.

Figure 10 is a sectional detail view of the protector disc.

The present cartridge comprises a substantial cylindrical metallic body 1, having formed therein an elongated gas chamber 2. The discharge end of this cartridge is not herein shown since it forms no part of the present invention, but it is to be understood that the usual form of discharge assembly, such as is shown in the cospending application of Ferrell et al., Serial No. 169,441, tiled February 19, 1927, may be used. This assembly, of course, consists of a disc positioned over the discharge opening in the end of the cartridge,

a shear ring backing up the disc and a discharge cap having threaded engagement with the cartridge body and bearing on the shear ring to exert pressure therethrough to seal the disc against the end of the cartridge.

The opposite end of the cartridge is provided with a transverse wall 3 through which there is formed a central aperture 4. Inwardly of the wall 3 there is formed a substantially cylindrical pocket 5 which is in direct communication with the interior of the gas chamber. This pocket is threaded for a. portion of its length as indicated at 6. An electrode 7 extends through the aperture 4 of the wall 3 and is provided with a radial flange 8 which is adapted to be positioned adjacent the inner' face of the wall 3. The electrode is separated from the body of the cartridge by means of an insulator 9. Surrounding the end of the electrode which extends into the gas chamber' is a supporting and clamping nut 10 which has engagement with the thread 6 formed in the body of the cartridge. The nut 10 is provided with asquared or hexagonal portion 11 by means of which it may be screwed into the cartridge to exert pressure on the electrode to seal the same against the inner face of the wall 3. An insulating sleeve 12 is interposed between the electrode and the electrode nut 10. The extreme inner end of the electrode is provided with screw threads which enter into a screw threaded pocket formed in the end of a heater support 14. The heater support is provided with a pocket 15 for the reception of a heater unit and a flared approach 1G to facilitate the entry of a heater unit in the pocket. Suitable notches 17 are formed in the heater support for the reception of a wrench or the like whereby the support may be assembled on the inner end of the electrode.

lIhe electrode is provided with an axial passage 18 extending from the outer end thereof inwardly to a po-int within the gas chamber 2 and a transverse passage 19 extends from the passage 18 to the exterior of the electrode whereby to place the passage 18 in communication with the gas chamber. The outer end of the electrode is provided with screw threads 20 for the reception of a,

valve cap 21 which is sealed and insulated with respect to the body of the cartridge by means of a fibre disc 21. The outer end of the electrode is provided with a slight shoulder 22 surrounding the open end of the gas passage 18 and a valve 23 is designed to cooperate with the shoulder 22 for controlling the admission of uid into the passage 18. Valve 23 is screw threaded centrally through the portion 23 of the valve cap and at its inner end is provided with an enlarged head 24 which cooperates with a series of fibre packing discs 26 for the purpose of sealing against the escape of gas around the valve when the latter is in open position. The inner end of valve 23 is provided with a soft metallic insert 25 which forms a seat for cooperation with the shoulder 22 on the end of the electrode. The valve cap 21 is formed with a nozzle seat 27 and a communicating passage 28 leading into the interior thereof.

The outermost end of valve 23 is of rectangular form in order that a wrench may be applied thereto for operation of the valve. This portion 29 is provided with an axial bore 30 designed to receive a. contact plug 31.

The insulating hcat'32 of the contact plug A is of such size as to be readily insertable through an aperture formed in the protector dise 34.

The outer end of the electrode and the entire valve assembly hereinabove described are housed within a cuplike extension of the cartridge body, the bottom of which is formed by the outer face of the transverse wall 3. In order to protect these elements there is provided the protector disc 34 which is screw threaded into the end of this extension as in dicated at 33. This disc is provided with a central aperture 35 and an offset aperture 36, the latter being positioned in alignment with the nozzle seat 27 formed in the valve cap. These apertures 35 and 36 are provided with cover plates 37 and 38 respectivelyT which are pivotally mounted on the protector disc as indicated at 41 and 42. In order to prevent accidental displacement of these cover plates, they are provided with dependent lugs 37 and 38 respectively which are designed to snap into their respective apertures and hold the plates firmly in position.

Referring particularly to Figures 6 to 9 inclusive, it will be noted that the contact plug hereinabove briefly described comprises merely a metallic body portion 43 and an insulating head 32. Extending from end to end of the metallic body there is provided an axial bore 45 and intersecting this bore there is a transverse slot which extends for approximately one-half the length of the plug. It will be noted from Figure 7 that the width of the slot is slightly less than the diameter of the bore. The principal reason for this relation is that the use of a wire of substantially the diameter of the bore will serve to spread the two prongs of the contact plug at each application. The wire is first passed entirely through the plug from the head end thereof and is then drawn laterally through the transverse slot 46 thereby expanding the prongs of the plug. It will be noted that the slot 46 extends slightly beyond the enlarged portion of the plug in order that the wire may be drawn beyond this enlarged portion and wrapped around the periphery thereof. The fibre or other insulating head 32 may be secured to the plug in any desired manner, but, as herein shown, it is proposed to countersinlr the head end of the plug body and peen over the edge thereof adjacent to the fibre head 32.

Referring again to Figure 1 of the drawings, it will be observed that there is normally an open circuit between the electrode and the body of the cartridge and that by reason of the protector disc it is practically impossible to bring about an accidental discharge of the cartridge through contact of the electrode with a source of electricity. Another of the important features of the present construction is the valve mechanism herein shown. By virtue of the packing interposed between the head of the valve and the wall of the pocket formed in the valve cap, it will be readily understood that an effective seal is provided around the valve during a charging operation. The further outwardly the valve is moved, the greater will be the sealing effect thereon. The improved contact plug is also of considerable importance in view of its simplicit-y and etfectiveness. It will be noted that when the cartridge is to be discharged the plug may be inserted in the end of the valve member and thereafter the cover plate 37 may be moved to partially close the opening 35 A and thereby prevent accidental withdrawal of the plug.

I claim:

1. A blasting cart-ridge embodying a gas chamber and a pocket separated by a division wall, an electrode extending thru and insulated from said wall and having its ends disposed in said gas chamber and pocket respectively, said electrode having a gas passage therethru, valve mechanism disposed within said pocket and operatively associated with an end of said electrode, said valve mechanism being constructed to receive a contact plug and a charging nozzle, a closure` for said pocket having apertures to permit the insertion of a contact plug and charging nozzle respectively, and means for closing said apertures.

2. A blasting cartridge comprising a substantially cylindrical metallic body having a gas chamber formed therein` said body having a substantially cylindrical open pocket in one end thereof which is separated from said gas chamber by a transverse division wall, an elect-rode extending thru and insulated from EXPLOSIVE DEVICES said wall and having its ends disposed in said pocket and gas chamber respectively, a valve body disposed within said pocket and operatively associated with said electrode, said electrode having a passage therethru, a Valve adjustably mounted in said valve body and adapted to cooperate with the end of said electrode and passage, a closure for the end of said pocket having openings therethru to permit the insertion of a charging device for cooperation with said valve body and an electrical contact device for cooperation with said valve and means for closing said openings.

3. A blasting cartridge embodying a gas chamber and a pocket, an electrode extending from said chamber into said pocket, a closure for said pocket having an opening in alignment with said electrode and a contant plug adapted to be inserted thru said opening to establish electrical connection with said electrode, said closure having means adapted to close said opening when said contact plug is in place to prevent accidenta withdrawal of the plug. I

4. The combination with a blasting cari` tridge having a gas chamber and an element extending into said chamber and having a gas passage therethru to permit the introduction of gas into said chamber, of a valve mechanism associated with said member and including a body, a valve stem having threaded engagement with said body, said valve stem having a head adapted to engage the end of said member and seal the gas passage therein and a packing surrounding' said stem and adapted to be compressed between said head and body when the valve stem is screwed outwardly, whereby to prevent escape of gas around the threads of said stem and body.

5. A blasting cartridge embodying a gas chamber and a passage for the introduction of gas into said chamber, a valve stem adapted to be adjusted toward and from an end of said passage and means operative by retraction of said stem to seal against escape of gas around the stem.

6. A blasting cartridge embodying a gas chamber, an electrode extending into said chamber and insulated from the cartridge, said electrode having means in electrical connection therewith provided with a bore, a detachable contact plug adapted to engage said bore, said plug comprising a metallic body having an axial bore therethru and a longitudinal slot, the diameter of said bore being greater than the width of said slot.

7. A blasting cartridge comprising a substantially cylindrical metallic body having a gas chamber formed therein, said body having a substantially cylindrical open pocket in one end thereof which is separated from said gas chamber by a transverse division wall, valve and electrode means within said pocket and having effective com- 

